Create + Edit Product Screens

Two-step wizards. Create: 975-line composite of basic info → options matrix → variant pricing → image upload. Edit: same form prefilled, plus an inventory-quantity per variant input.

1. Create: pickCategory → setTitle/desc → addOption × N → fill variant prices → upload images → submit.
2. Edit: load existing product → modify any field → submit triggers updatePhysicalProduct + setInventoryItemQuantity for changed variants.
3. Image picker uses image_picker; uploaded URLs are appended to product.images.

• Editing options after variants exist is risky — the matrix re-builds, but server may refuse if existing variant.value strings no longer fit.
• Currency change is allowed in edit but rare — UI shows a warning.
• Long-press on a variant offers a 'duplicate' helper to copy price into adjacent variants.

• lib/src/features/seller/products/views/create_product_screen.dart
• lib/src/features/seller/products/views/edit_product_screen.dart

Create screen is 975 lines — a good candidate for splitting into step-widgets but not blocking shipping.